1. Field of the Invention
This invention relates to a method for printing on a molded body of a thermoplastic synthetic resin and a headphone housing on the surface of which printing has been made by the printing method.
2. Description of the Related Art
Heretofore, as a method for printing on a molded body of a synthetic resin, such as an inner ear type headphone housing or a keytop of a keyboard device, a printing method such as a silk screen printing has been extensively applied. The silk screen printing method includes the steps of transfer printing a letter, character or a figure on the surface of a synthetic resin molded body with a thermosetting ink, such as an epoxy resin, white pigment or a silver white pigment, and heat setting said ink for burning and printing the letter etc. on the surface of the molded body.
With the letter or figure, obtained by such printing method, since the thermosetting ink is simply applied to the surface of the molded body, it is easily abraded by friction or peeled off during handling and thus becomes hardly visible.
For overcoming such inconvenience, there is also known a printing method which makes use of a laser light. With this method, a coating of aluminum, for example, is formed on the surface of a synthetic resin molded body by vacuum deposition and the coating is irradiated with the laser light for selectively removing the coating after the contour corresponding to the desired letter, figure etc. to expose the underlaying surface of the molded body to effect printing.
There is additionally known a printing method in which the surface of the synthetic resin molded body is irradiated with a laser light to remove the surface of the molded body by engravure so that removed portions represent a predetermined letter, figure or the like.
With these prior-art printing methods by the laser, printing with excellent abrasion resistance and durability may be achieved. However, with the printing method in which the aluminum coating is applied on the surface of the molded body and the coating is selectively removed by engravure for printing, the printing process is complex and expensive. On the other hand, with the printing method of removing the surface of the molded body by engravure, the printing is of the same color as the molded body and hard to see or indistinguishable from the background.